Servo system



Patented May 27, 1941 2,243,626 I C E 2,243,626 SERVO SYSTEM David Greg Caldwell, and Richard Daalder, Paterson, N. J., assignors to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Original application December 211, 1938, Serial No. 247,120, now Patent No. 2,205,354, dated June 18,

Divided and this application December 20, 1939, :Serial No. 310,246

, *3 Claims.

This invention relates to servo-systems, and

particularly to the structure and operation of a servo-element forming part of a fluid pressure system, and operable in response to fluid pressure to control the performance of the power plant (engine, motor, or the like) to which it is applied.

'This application is a division of our applica tion No. 247,120 filed December 21, 1938, and issued as Patent No. 2,205,354 on June 18, 1940.

The invention involves use of a pressure actuated servo-motor including a piston adapted to receive operating fluid on opposite sides thereof under the control of a valve adapted to be shifted by manual means, as well as by movementof an expansible element (herein shown as a bellows) whose interior is in communication with a fluid supply passage of the power plant to be governed,

.and therefore reflects the pressure conditions prevailing therein; the latter mode of operation being hereinafter referred to as the automatic control.

An object of the invention is to provide means for locking out the automatic control elements at the will of the operator, with the manual control continuing to function independently of any movement of said automatic control elementseven during the actual process of locking out said automatic elements.

A further feature is the provision of manual control of the power plant performance by com trolling the degree of resistance ofl'ered to expansion of the expansible element; said manual control being herein disclosed as incorporated in the same control linkage as that which governsthe locking out of the piston, although (as will appear) it may be separate and distinct therefrom,

and operated independently thereof.

' These and other objects and features of the invention are pointed out in the following description in terms of the embodiment thereof which is shown in the accompanying drawing. It is to be understood, however, that the drawing is for the purpose of illustration only, and is not designed as a definition of the limits of the invention, reference being had to the appended claims for this pu p se.

In the drawing,

Fig. 1 is a schematic representation'of the invention as applied to the control of the combustible mixture for an internal combustion engine; and v Fig. 2 is a diagram showing certain of the parts in positions which differ relatively from those in which the corresponding parts are shown in Fig. 1.

In the drawing, reference character 5 designates a diagrammatic showing of the intake manifold of an internal combustion engine whose crank-shaft or other power shaft (not shown) drives a supercharger 6 through suitable mechanical connections of which those shown at 1 and I may be considered illustrative. The manifold 5 serves to connect carburetor 8 with the combustion spaces (not shown) of the engine, by way of supercharger 6 and supercharger inlet 9; the throttle I0 being pivotally mounted in said inlet passage 9, and shiftable to any position. be-

corresponding movement of the linkage leading thereto. This linkage includes a manually shiftable throttle control lever II and a bell-crank I2 whose central pivot l3 passes through the end portion I4 of a rod [5 whose opposite end is integrated with a piston I9 constituting the servoelement above referred to.

As shown the servo-piston i6 is slidable in a cylinder i'l having two ports l8 and I9 on opposite sides of said piston, through which ports fluid is caused to flow whenever the correspondingly spaced covering portions 2| and 22, respectively, of the slide valve 23 are not in flow inhibiting relation thereto. The operating fluid may be oil received from the engine oil supply by way of pipe 26 and returnable to the engine oil sump by way of outlet 28 or 29, as the case may be, whenever a shifting of the control valve 23 from its neutral position causes one of said outlets to receive 011 discharged from the cylinder IT.

The disclosed embodiment of manifold pressure actuated means acting upon control valve 23 to cause supercharger regulating (throttle shifting) movement of the servo-element IE will now be described. An arm 3| extends in rigid fashion from one end of valve 23 and connects to a plate 32 interposed between a pair of hollow, flexiblewalled cylinders or bellows 33 and 34, the former being sealed under vacuum or under a predetermined pressure-although a vacuum or near vac uum is preferred. Bellows 34, on the other hand, has direct communication with intake manifold 5 by reason of conduit 36 leading thereto, and

. also contains a tube 3l"and='spring 38- having one end thereof fastened to the end portion 39 of the tube 31; the opposite end of spring 38. being secured to the end portion or collar 4| of a rod 42 constituting part of the manually operable means 1 64, 14 and 84 for looking out the piston I6, and

The range of movement of this linkage 64 to 42 (as indicated by the arc ABC-D in the drawing) thus determines the maximum and minimum limits of manifold pressure obtainable by the automatic means constituted by servopiston IE; it being understood that the piston l4 can move only in response to a shifting of the control valve 23 in either direction from its central position, and that the action of the control valve 23 is in turn governed by the extent to which spring 38 or the existing manifold pressure may temporarily over-power the other and thus cause a temporary shifting of the valve 23 from said central position.

The looking out of the servo-element I6, when desired, is accomplished in either one (or both) of two ways:;-flrst, by the establishment of a fluid lock, which involves manually shift- 'that one extreme coincides with the fluid lock establishing position of the valve shifting rod 42;

the result of such coincident settings being, of

course, to make it. possible to have both the fluid lock and the mechanical lock effective in such manner that the latter supplements and confirms the former. v

The manner in which these two locking actions are effected will now be described in greater detail. First, as to the fluid lock, this can not occur until the movement of rod 42 is sumcient to bring the collar 4| thereof into abutting engagement with the end of tube 31. After such abutting engagement occurs, further movement in the same direction will result in corresponding shifting of the valve 23 (to the position shown in the drawing) due to the rigid connection between valve arm 3i and the plate 32 with which tube 31 is integrated. Such shifting of valve 23 will uncover outlet is and will thus remove all oil actions may, of course, be dissimultaneous; that is, the controlling cam 83 may be in either end zone prior to movement of groove 62 to the latch receiving position; but in such event the latch will bear frictionally upon the adjacent portion 10 of the sliding rod II until the groove 42 arrives opposite the latch, whereupon the latter will snap into locking position-assuming that in the meantime the operator has not shifted control cam 63 to an intermediate (BC) positionand thereby provide positive restraint against movement of the piston ll, over and above the resistance to such movement that is due to the pressure of the oil and the spring 40 upon said piston, in this fluid lock" position of valve 23.

With the piston thus locked the operator may exercise full manual control over the throttle by manipulation of throttle lever H, as above 1 described.

Y and a valve controlling delivery of pressure fluid During periods when there is nolock-out of the rod II, the throttle may be shifted by either the manual means II or by movement of the piston, for-as in the prior art-the bell-crank I2 is of the floating type, with both its central pivot l3 and its upper pivot I 30 serving alternately as fulcrums about which rotatipn may occur; the pivot i3 being the fulcrum wherein manual actuation occurs, and the pivot "a when automatic (piston induced) actuation occurs. In

this connection it is to be understood that the levers H and 64 are held, frictionally or otherwise, in whatever position they are caused to occupy, and remain in such positions until manually shifted.

What is claimed is: v 1. The combination with a piston rod, a piston,

to said piston for movement of said rod, fluid pressure responsive means for shifting said valve in one direction, means opposing said fluid pressure responsive means, manual means for inpressure resistance to movement of piston IE to v its innermost position, under the urge of the oil pressure on the outer side of the piston, into which oil is now being supplied by way of ports 26 and i9; the movement of the piston to its innermost position being further assured by rea- I means 64) in either of the end zones ("A-B or' CD) of its range of movement, the entire range of movement being that indicated by the arc A-D as a whole; and secondly, the completion of the inward stroke of the piston whereby groove 62 of the piston rod arrives in position to receive latch Si and be held firmly thereby, by reason of the pressure exerted in the locking direction by spring 3. These two creasing the effectiveness of said opposing means, and a latch engaging said piston'rodinresponse to a predetermined degree of movement of said manual means.

2. The combination with a piston rod, a piston, and a valve controlling delivery of pressure fluid to said piston for movement of said rod, manual means for shifting said valve, means engageable with said rod to lock the piston against movement, said locking means being operable in response to a predetermined degree of movement of said manual valve shifting means, means movable with said manual means to release said locking means from engagement with said rod, and fluid pressure responsive means for shifting said-valve, said last named valve shifting means being inefl'ective until release of said locking means.

3. The combination with a piston rod, a piston, and a valve controlling delivery of pressure fluid to said piston for movement of said rod, fluid pressure responsive means for shifting said valve in one direction, a spring opposing said fluid pressure responsive means, manual means for increasing the opposing force of said spring, and a latch engaging said piston rod in response to a predetermined degree of movement of said manual means.

' DAVID GREGG.

RICHARD DAALDER, 

